Prefabricated radiation safe window adjustable for mounting in biological shields of different thicknesses



3,433,957 MOUNTING SES arch 1. 1969 w NELSON PREFABRIGATED RADIATION SAFE WINDOW ADJUSTABLE FOR IN BIOLOGICAL SHIELDS OF DIFFERENT THICKNES Filed 001; 14, 1965 INVENTOR. W/LFRED W. NELSON TORNIEYS I HOT SIDE

United States Patent 9 Claims Int. Cl. G21f 7/00; E06b 3/60, 3/32 ABSTRACT OF THE DISCLOSURE A prefabricated radiation safe window for biological shields is described which is adjustable to permit its incorporation into biological shields of different sizes. The window includes a casement having a raised window jamb and an outwardly flared encircling apron structure extending from one side of the casement for overlapping relationship with a biological shield wall into which the window is to be mounted. Radiation absorbing material such as lead extends from the inner periphery of the easement and along the outwardly flared portion thereof to provide a continuous absorbing structure from the shield wall to the Window opening in the casement. A plurality of spaced anchor grooves are provided along the inside periphery of the casement at a position spaced outwardly from the Window jamb, and pane retainer spring clips are adapted to cooperate with the grooves to permit radiation absorbing window panes of different thicknesses to be secured within the casing. A rim member is telescopically mated with the casement on the side thereof opposite the apron structure so that the frame can be mounted in biological shields of different thicknesses.

This invention relates to an observation window through which areas containing objects or equipment having unsafe ionizing radiation levels may be safely observed. More particularly, the invention relates to such a window which is prefabricable and yet is adaptable for use in different installations of various requirements and which has a replaceable pane so that the pane can be changed when changes occur in the radiation level in the area being observed.

In working with objects or equipment having unsafe ionizing radiation levels, it is necessary that personnel be protected by a biological shield to lessen the radiation hazard to them. Typically, personnel are protected by placing an absorber between the personnel and the radiation source. Absorbers are material Which asborb or stop ionizing radiations, such as strong neutron absorbers like boron, hafnium and cadmium or the more common absorbers like lead, concrete and steel which are often used to attenuate electromagnetic radiation, gamma radiation and neutron radiation in biological shields. Alpha and beta particles (radiation) are more easily stopped, the latter by thin sheets of metal and the former can be stopped by thin sheets of paper. These absorbers substantially eliminate or reduce radiation hazards to personnel working around such radiation.

Since ,the maximum safety tolerances for total whole body radiation absorbed by personnel working with ionizing radiation are: gamma or X-ray radiation, 0.1 roentgen per eight hours; beta radiation 0.5 roentgen per eight hours; neutron radiation 0.014 roentgen per eight hours; and alpha radiation in air, micro-micro-curie per liter of air, it is important that personnel have adequate biological shielding.

A serious problem arises in providing the proper shielding precautions when the personnel must have visual observation of areas having objects or equipment having un- 3,433,957 Patented Mar. 18, 1969 safe ionizing radiation levels. Such visual observation is often necessary where radiological medical treatment is being carried out, such as the treatment of cancerous tissue with X-rays or radioactive isotopes. Also, where personnel are using manipulators (mechanical devices for handling radioactive materials) which are remotely controlled from behind biological shielding, direct visual observation of the areas is desirable. Of course, there are other circumstances wherein visual observation of areas having unsafe ionizing radiation levels is desirable for technical and operating personnel working with objects or equipment producing unsafe radiation.

One approach to provide safe visual observation of areas having unsafe ionizing radiation levels is the use of indirect viewing, such as could be accomplished through closed-circuit TV and the other approach is through radiation safe windows wherein direct viewing of such areas is possible. In many situations direct viewing through radiation safe windows is preferred since it offers considerable advantages over indirect viewing, such as that obtained with TV monitors. The principal advantage in direct viewing through radiation safe windows occurs when personnel are operating and/or moving objects on the remote or radiation hot side of shield since they can more easily determine relative movement and distances by direct visual observation. This invention relates to the latter approach, that of direct visual observation through radiation safe windows.

Radiation safe windows often consist of a frame with the appropriate shielding incorporated therewith and a viewing glass or pane containing a substantial quantity of absorber material, such as lead. Of course, glass containing lead (leaded glass) is not as an efiicient absorber as pure lead and thus the equivalent absorbing thickness of such glass is many times greater than that of pure lead. Further, the thicker the viewing glass or pane in the window, the greater is the optical distortion for the visual observer looking through the glass. Thus, the thickness of the viewing glass or pane should be minimized where possible, so long as unsafe radiation levels will not reach the observer.

A common problem in many radiation safe windows for observing areas having unsafe levels of ionizing radiation is that the window is chose-n to be of sutficient thickness to stop the maximum radiation level which might occur and therefore these Windows cause unnecessary visual distortion at lower levels of radiation Where thinner viewing glass or panes would be satisfactory. Furthermore, most radiation safe window frames are now custom made for each individual installation because of the difficulty in providing a properly shielded frame which can be accommodated to dilferent installations.

Accordingly, an object of the present invention is to provide a radiation safe window having a replaceable pane so that the thickness of the pane may be chosen to provide adequate protection against radiation with minimum optical distortion for the visual observer looking through the pane.

It is also an object of the invention to provide a radiation safe window in which the frame is properly shielded and yet is adjustable for installation in shielding of different thicknesses.

Another object is to provide a radiation safe window wherein the pane is replaceable by higher quality absorbers, such as sheets (panes) of lead, when high ionizing radiation levels are to be experienced and visual observation is not practical.

A further object is to provide a radiation safe Window in which the viewing glasses or panes can be interchanged therebetween and/or switched with higher quality opaque absorbers without any loss of flexibility to save the expense of acquiring numerous expensive transparent panes.

Also, it is an object of the present invention to provide an inexpensive, adjustable, prefabricated radiation safe window with interchangeable panes which can easily be installed in a biological shield to provide convenient visual observation through the shield.

One other object is to provide a radiation safe window with contiguous, radiation-safe direct voice communication therethrough which is especially useful for medical technicians subjecting patients to ionizing radiation for medical purposes.

Still another object is to provide a radiation safe window having no radiation exposed mounting slots, holes or the like on the side of the window having unsafe ionizing radiation levels.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted Within the scope of the invention as set forth in the claims.

FIGURE 1 is a vertical section through the lower portion of the radiation safe window taken along lines 1--1 of FIGURES 2 and 3 showing the internal detail of the window.

FIGURE 2 is a perspective of the back or radiation hot side of the radiation safe window mounted in a biological shield.

FIGURE 3 is a perspective of the front or radiation safe side of the same window as shown in FIGURE 2.

For convenience, in the description of this invention reference will be made to the hot and safe sides of biological shields which refer to the side having unsafe ionizing radiation levels and the side the operating personnel are safe from such radiation hazards, respectively.

More specifically, the invention can be more easily understood by referring to FIGURE 1 showing the lower portion of the radiation safe window in vertical section. Since the top of the window is almost identical with the lower portion, with the exception of the voice tube, only the lower portion will be specifically described. In FIG- URE l the radiation safe window is shown mounted in a double walled biological shield 11. The hot side of the shield 11 consists of a laminated wall 12 having a layer of high quality absorbing material 13, such as lead, sandwiched between two outer layers 14 of concrete. The safe side of the shield 11 is a single concrete wall 15 which is spaced a short distance from the laminated wall 12.

In the type of biological shield described above, a window support member 16 is fastened with several flush head bolts 17 between the two spaced walls 12 and 15, respectively, to provide a support ledge 18 for attaching the window 10 in the shield 11. Normally the support ledge 18 is an inward projecting horizontal flange or ledge at the base of the rectangular port 19 in wall 15 for the window. A similar but larger rectangular port 20 is made in laminated wall 12 so the two ports are generally aligned so the radiation safe window of this invention can be installed. Any suitable window support member providing such a flange or ledge could be used and the support member 16 shown in the drawing is merely an illustrative embodiment.

Next, considering the radiation safe window 10 itself, it has an outer rectangular casement 21 which is generally boxshaped without a top or bottom. At the inboard edge 22 of the outer casement is a raised window jamb 23 which projects inwardly around the inside of the periphery of the outer casement 21 to form a jamb abutment for a pane 24 which is cut to just fit inside the outer casement. The pane 24, which is or contains radiation absorbing material, is held against the window jamb 23 by spring clips 25 which have an end anchored in one of the plurality of parallel spaced clip retaining grooves 26 on the contiguous inside faces of outer casement 21. In the embodiment shown, each of the spring clips 25 extend completely along one peripheral inside edge of the easement and its ends are mitered to provide a smooth joint with the adjacent clips. Thus, the clips provide a molding of pleasing appearance completely about the pane. However, it is to be realized that in those installations requiring frequent interchanging of panes, the clips 25 can :be of a less length than the peripheral edges of the window and be designed for easy removal by finger pressure.

A plurality of retaining grooves 26, are provided around the inside faces of the outer casement, each set being spaced a different distance from the jamb.'Bccause of such, different thicknesses of panes can be-accommodated by the frame. That is, when it is desiredto place relatively thick panes inside the outer casement 21, the grooves more remote from the jamb 23 can be used for the clips and when thinner panes are to be used, the clips can be retained by the grooves closer to the jamb.

Connected to the inner periphery of the inwardly projecting window jamb 23 is the inboard edge of an inner rectangular casement 27 which is similar to the outer casement 21 but has smaller inside dimensions than the outer casement 21 so that the inner casement will be attached on the inner peripherial edge 28 of jamb 23 and inwardly stepped up from the inside faces of the Outer casement as can be seen in FIGURE 1.

On the outboard edge 29 of the inner casement 27 are a plurality of outwardly diverging aprons 30 of a flat sheet metal construction. Aprons 30 have their contiguous edges 31 mitred and joined with a bead weld so that the appearance of the window; looking from the hot side toward the safe side, is that of a funnel-shape, opening outwardly away from inner casement 27. The outboard edge 32 of this generally rectangular, a funnel-shaped apron structure is squared off in a plane parallel with the faces of pane 24 and has an outwardly flared flange 33 circumscribing its entire periphery. The faces of the flange 33 are also oriented in a plane parallel to the faces of pane 24 and inboard face 34 of the flange is designed to overlap the sides of the rectangular port 20 in the laminated wall 12 made for receiving the window 10 so the flange will bear on the wall surrounding the port when the window is mounted in biological shield 11, as can best be seen in FIGURES 1 and 2.

In the embodiment of the window 10 shown in FIG- URE 1 the inboard face 34 of flange 33 has inwardly projecting therefrom a combined aligning rib and cladding (absorber material) support 35. The aligning rib 35 has a flat bearing face which is designed to fit flatly against the hot side of wall 12 around port 20 when the window 10 is inserted in this port provided in the biological shield 11 for the window.

The cladding or absorber material 36, which is usually lead, is shown in FIGURE 1 as a complete liner on the blind sides of flange 33, aprons 30, inner casement 27 and window jamb 23. All the cladding is joined at the intersection of these parts so there is one continuous sheet of absorber material behind the cladded structural parts of the radiation safe window 10. Looking closely at FIGURE 1 it can be appreciated that the continuous liner of cladding 36 on the blind side of the structural parts of the window, because of the unique structural features of the window 10, provides an overlap with the absorber material 13 within the laminated wall 12. Thus, ionizing radiation cannot pass from the hot side through either the shield 11 or any structural portions of the window 10, except the opening of the inner casement 27 closed by pane 24, without hitting absorber materials 14 or 36. Of course, since window pane 24 is usually selected from transparent material containing absorber materials and is of sufficient thickness to stop the level of ionizing radiation being experienced on the hot side of the window 10,

the window is safe for personnel to observe therethrough areas having unsafe ionizing radiation levels.

The remaining principal structural element of the radiation safe window is a rectangular rim member 37 closely fitting in an overlapping relationship around the outside periphery of the outer casement 21 and so it can telescope thereon. The rim member 37 also contains an outward projecting flange 38 having faces parallel with the faces of pane 24 and which overlap the port 19 in wall 15 of the biological shield 11 for receiving the window while the telescoping portion of the rim fits into the port 19 as it slides over outer casement 21. Since rim member 37 telescopes over outer casement 21 the rim member can be slidably moved on the outer casement 21 to accommodate biological shields of varying thicknesses.

Normally, the radiation safe window is mounted in the openings in a biological shield, such as shield 11, from the hot side with the rib 35 on the inboard face 34 of flange 33 flush against the hot side of the shield around port 20. Then the rim member 37 is fitted over outer casement 21 from the safe side of the shield and slidably moved inboard into port 19 and over the outer casement 21 until the inboard face of its flange 38 abuts on the outside of the safe wall of the shield around port 19 and sandwiches the shield between flanges 33 and 38 on opposite sides of the shield. When this has been accomplished a hole is drilled from the inner face of outer casement 21 through the outer casement, the overlapping portion of the rim member 37 and through flange 18 of the support 16 anchored in the shield 11. A self-tapping screw 39 is then inserted in the drilled hole and screwed down into the hole so it will pass through all the members. The screw 39 passing through the outer casement 21, the rim member 37 and the flange 18 locks these parts together and secures the window in the shield. It is apparent from the drawings that there are no holes, slots or the like on the hot side of the shield 11 for retaining window 10 in the shield when the above described mounting is used. This prevents any chance of radiation leakage through the window through such mounting holes, or the like.

The only structural element of the radiation safe window 10 not previously described is the incorporated voice tubes. This feature is useful when the window is being used by medical technicians where they must orally communicate with patients on the hot side of the biological shield. Each of the voice tubes themselves are composed of rectangular or box-shaped conduits 40 and 41 which are joined at right angles to form a continuous right angle conduit 42. These right-angle conduits 42 are incorporated into radiation safe window 10 in the base thereof and, when used, have conduits 40 resting on flange 18 so that rim member 37 can slide between the tops of conduits 40 and the bottom of outer casement 21 when it is being adjusted for the thickness of the shield 11. Under these circumstances the self-tapping screw 39 may also pass through conduits 40 when the window is locked in the shield by inserting the screw.

In flange 38 of rim member 37 two small rectangular ports 43 are provided contiguous to the outboard ends of conduit 40 to provide openings for sound communications into conduits 40. At the opposite end of voice tubes two rectangular ports 44 are provided in the base of the inner casement 37 and also through cladding 36 for the conduits 41 to fit into. Through the use of the ports and right-angle conduit 42 direct oral communication can be carried out between the safe and hot sides of the shield 11 without radiation hazzard to personnel on the safe side of the window 10.

Because of the set back of inner casement 21 from the wall 12 on the hot side of the shield 11 and the geometry of the window construction, no straight line path exists through the window (except through the window pane) that radiation could leak through even though small portions of cladding 36 are removed for the Voice tubes right-angle conduits 42 to pass through. Staggered plates of absorber material (not shown) could be added to the top of conduits 41 to stop radiation if this somehow becomes a problem. Further, if alpha particles are present, a thin, transverse air-impervious diaphram can be installed in the right-angle conduits 42 to prevent air circulation without seriously impairing voice communications.

What is claimed is:

1. A prefabricated radiation safe window for mounting in biological shields for visual observation therethrough comprising a casement having a raised window jamb and a plurality of spaced anchor grooves around its inside periphery, said anchor grooves being outwardly spaced from said jamb, spring clips adapted to be retained in said grooves selectively in different spaced relations to said jamb to hold selective radiation absorbing window panes of corresponding different thicknesses in abutment with said jamb, an outwardly flared encircling apron structure extending from one side of said casement for overlapping relationship with a biological shield wall into which said window is to be mounted, said apron structure including radiation absorbing material extending from the inner periphery of said casement and along the outwardly flared portion thereof to provide a continuous absorbing structure from said shield wall to the window opening in said casement, and a rim member telescopically mated with said casement on the side thereof opposite said apron structure for adapting the frame for biological shields of varying thicknesses.

2. The radiation safe window of claim 1 wherein the apron structure includes a protruding flange on its outboard edge which will overlap the opening in the shield on its side of said window and in against one wall of said shield and the rim member includes a similar protruding flange which will overlap the shield on the opposite side of said window so said shield is sandwiched between said flanges on each side thereof when said window is mounted in said shield.

3. The radiation safe window of claim 2 wherein the wall overlapping flange on the encircling apron structure is cladded with absorber material to provide an overlap of absorber material in the shield and in said window.

4. The radiation safe window of claim 2 wherein a mounting flange is anchored to the wall, and the rim member and casement are fastened to one another and the flange when the shield is tightly sandwiched between the overlapping flanges on opposite sides of said shield.

5. The radiation safe window of claim 2 wherein the absorber material is lead sheeting.

6. A prefabricated radiation safe window for mounting in biological shields for visual observation there through comprising a casement having a raised window jamb and including retainer means for maintaining a radiation absorbing window pane in abutment with said jamb, an outwardly flared encircling apron structure extending from one side of said casement for overlapping relationship with a biological shield wall into which said window is to be mounted, radiation absorbing material extending from the inner periphery of said casement and along the outwardly flared portion thereof to provide a continuous absorbing structure from said shield wall to the window opening in said casement, and a rim member telescopically mated with said easement on the side thereof opposite said apron structure for adapting the frame for biological shields of varying thicknesses.

7. The radiation safe window of claim 6 wherein the rim member includes an outwardly protruding flange which will overlap the opposite side of said biological shield, and fastener means are provided on the safe side of said window for securing said casement and rim together to sandwich said biological shield between the overlapping flanges on opposite sides of said shield.

8. The radiation safe window of claim 6 wherein ports are provided in the inner casement and in the rim member and connected with right-angle conduits to provide voice communication through said window.

9. The radiation safe window of claim 6 wherein the retainer means comprises a plurality of spaced anchor References Cited UNITED STATES PATENTS 2/1934 Smidt 52502 9/1965 Felix et a1 52476 8 3,283,156 11/1966 Mazza.

RALPH G. NILSON, Primary Examiner.

SAUL ELBAUM, Assistant Examiner.

US. Cl. X.R. 

